There is a well-known need for an implantable glucose sensor in the treatment of diabetes. A continuous sensor would provide users a warning of hypoglycemia and information for improved insulin replacement either by conventional injection, mechanical insulin pumps or other means. We have a sensor that shows promise. The sensor employs immobilized glucose oxidase coupled to a potentiostatic oxygen electrode, operated in conjunction with an oxygen reference electrode. The sensor was developed over the last fifteen years using a systematic engineering approach. A simple version of the sensor has been employed as a central venous implant in dogs and has functioned for more that 100 days without the need for recalibration, the standing published record for long-term performance. The sensor has clear potential for operation as an implant for longer periods. However, in many cases, especially in children, a tissue site may be preferable for implantation. GlySens' goal is to produce a different type of glucose sensor for application in tissues. In this Phase I project we plan to: (1) make a prototype sensor based on adaptation of integrated circuit fabrication technology; (2) fabricate and validate prototype benchtop instrumentation to operate the sensor; and (3) characterize and test the sensor extensively in vitro. These studies will identify factors that affect sensor performance and lifetime. This work represents innovation over our previous sensor design and fabrication methods and is a necessary step toward commercial application. In Phase II, the sensor will be refined if necessary. PROPOSED COMMERCIAL APPLICATION: The management of diabetes consumes 15% of total national health care expenditures, 25% of MediCare expenditures, ad is responsible for an enormous, untold cost in human resources. These costs could be reduced substantially by better blood glucose control resulting from improved insulin replacement, made possible by continuous monitoring of blood glucose. There are several million people with diabetes who could benefit.